A survey of 647 likely Republican primary voters in Colorado showed that while nearly 40 percent of respondents were still undecided, more than a quarter are supporting Colorado Treasurer Walker Stapleton’s run for governor, giving him a slight lead over his fellow GOP competitors.

The primary survey conducted by Magellan Strategies was released Monday on the eve of precinct caucuses, in which Stapleton is not participating. Stapleton earned 26 percent of support, giving him a 13 point lead over Attorney General Cynthia Coffman (13 percent). Both these two candidates did well on image ratings, with Stapleton earning 33 percent favorable (13 percent unfavorable) among voters and Coffman earning 20 percent favorable (21 percent unfavorable).

“The fact is it’s still early in the Colorado Republican primary election for Governor,” the release said. “At this time, Walker Stapleton is the clear frontrunner with a 13-point lead over Cynthia Coffman. However, with 39 percent of likely voters yet to choose a candidate the outcome is far from certain.”

At least 43 percent of respondents are “immigration first,” which means they believe the top issue they want their candidate to focus on is enforcing the country’s immigration law. Among these “immigration first” voters, Stapleton (26 percent) once again edged out Coffman (11 percent). Nearly half of “immigrant first” voters are still undecided.

Voters polled have a very high rating of President Trump, with 82 percent of responders saying they approved of his job. Only 13 percent said they disapproved.

“The bottom line is the President is a rock star among the Republican base,” the release said.

According to their release, the automated voice recorded survey was conducted on Feb. 26 and Feb. 27. The survey has margin of error +/- 3.85 percent.